Solution polymerization

ABSTRACT

A composition useful as a catalyst in solution polymerization comprises (1) a barium, calcium and/or strontium alcoholate, (2) an organoaluminum compound and (3) an organomagnesium compound. (2) and (3) may be used as a complex with (1). The compositions can be used to polymerize ethylenically unsaturated monomers like butadiene, butadiene and styrene, and isoprene and heterocyclic monomers like oxiranes, thiiranes, siloxanes, thiatanes and lactams. The catalyst composition can produce polybutadienes and butadiene-styrene copolymers having a trans-1,4 content as high as 90%. The non-terminating features of the polymerization of this invention permit the preparation of functionally terminated butadiene based polymers and block polymers containing sufficient amounts of trans-1,4 butadiene units to crystallize.

This is a continuation of application Ser. No. 319,820 filed Nov. 9,1981 now abandoned.

This application is a continuation-in-part of prior copending patentapplication Ser. No. 124,373 filed Feb. 25, 1980, now U.S. Pat. No.4,302,568, granted Nov. 24, 1981.

This invention relates to compositions of (1) barium, calcium and/orstrontium alcoholates, (2) organoaluminum compounds and (3)organomagnesium compounds and their use as catalysts for the solutionpolymerization of ethylenically unsaturated monomers like butadiene,butadiene/styrene and isoprene and for the polymerization ofheterocyclic monomers like oxiranes, thiiranes, siloxanes, thiatanes andlactams.

BACKGROUND OF THE INVENTION

The use of dialkylmagnesium or alkylmagnesium iodide in combination withbarium ethoxide particularly additionally with 1,1-diphenylethylene asinitiators of polymerization of butadiene to give polybutadiene having atrans-1,4 content as high as 78% and a vinyl content of 6% has beendisclosed by the Physico-Chemical Research Institute, Polymer ScienceU.S.S.R., 18 (9), 2325 (1976). This paper, also, shows that a catalystsystem of magnesium and barium tert-butoxide gave a polybutadiene withonly 45% trans-1,4 content (200 hours polymerization time and conversionof only 10%).

U.S. Pat. No. 3,846,385 (U.S. Pat. No. 3,903,019 is a division of thesame) shows the preparation of random butadiene-styrene copolymershaving a high trans-1,4 content and a vinyl content of 9%. The trans-1,4content increased as the mol ratio of Ba(t-BuO)₂ /(Bu)₂ Mg decreasedwith little variation in either the vinyl content or heterogeneityindex. A copolymer exhibited a well defined crystalline meltingtemperature at 32.6° C. by differential thermal analysis (DTA). TheMolecular Weight Distribution (MWD) of these copolymers wascharacterized by having heterogeneity indices (MHD w/MHD n) ranging from1.4 to 2.2. Polybutadienes made with these catalysts exhibited atrans-1,4 content as high as 78%. No polymerization or copolymerizationoccurred when only one of the catalyst components was used alone.

Polymerization of buadiene with some cyclization in hexane or toluene at100° C. using Bu₂ Mg-BuMgI is reported in "Chem. Abstracts," 1963,4045e.

Polymerization of butadiene using Ba(OEt)₂ with Et₂ Mg, (C₄ H₉)₃ Mg₂ Ior (C₆ H₁₃)₂ Mg is reported in "Chem. Abstracts," Vol. 84, 1976,151067n.

Dialkylmagnesium compounds and their complexes with organoaluminum orwith organolithium compounds are said to be cocatalysts with Zieglerbased catalyst systems (transition metal compounds) for thepolymerization of dienes and olefins. This has been described by TexasAlkyls (Product Data Sheet MAGALA-6E) and Lithium Corporation of America(Product and Technical Bulletin on "Polymerization Using Magnesium AlkylCatalysts," 1978).

British Patent No. 1,531,085 discloses in the working examples thepreparation of polybutadienes and butadiene-styrene copolymers havinginherent viscosities of 0.8 to 5, trans-1,4 contents of 34 to 90% andvinyl contents of 2 to 38%. A two component catalyst is used. As shownby the working examples the first component can comprise a Ba[Al(C₂ H₅)₄]₂, Ba[Al(C₂ H₅)₃ OR]₂ where R is a nonyl phenate radical, LiAl(C₂ H₅)₄,NaAl(C₂ H₅)₄, KAl(C₂ H₅)₄, LiAl(C₂ H₅)₃ OCH(CH₃)₂, LiOAl(C₂ H₅)₂compound and so forth. The second component is a polar compound or thelike such as tetrahydrofuran, methanol, water, tetramethylethylenediamine, acetone, barium nonyl phenate, lithium isopropylate,Na-tert-amylate, acetonitrile and so forth. The molar ratio between thepolar compound and the organic compound of metal of Group IIIA such asAl is from 0.01 to 100.

U.S. Pat. No. 4,079,176 discloses a process for polymerizing dienes andfor copolymerizing dienes and vinyl aromatic compounds with a catalystcomposition comprising (A) an organolithium and (B) a compound havingthe formula

    M.sup.a (M.sup.b R.sup.1 R.sup.2 R.sup.3 R.sup.4).sub.2 or M.sup.a [M.sup.c (R.sup.1).sub.4 ]

where M^(a) is Ba, Ca, Sr or Mg; M^(b) is B or Al; M^(c) is Zn or Cd;R¹, R² and R³ are alkyl or aralkyl radicals; R⁴ is an alkyl, aralkylradical or OR⁵ where R⁵ is an alkyl or aralkyl radical. The workingexamples show the polymerization of BD and copolymerization of BD withSTY to provide polymers exhibiting intrinsic viscosities of 0.81 to 1.6,trans-1,4 contents of 76 to 85% and vinyl contents of 2 to 6%.

U.S. Pat. No. 4,080,492 discloses a method for polymerizing BD orcopolymerizing BD and vinyl aromatic compounds using a catalyticcomposition of (a) an organolithium compound and (b) a cocatalyst systemwhich comprises a Ba or Sr compound and an organometallic compound fromGroups IIB or IIIA like zinc or aluminum. Examples of the Ba or Srcompounds are their hydrides, organic acid salt, alcoholates, thiolates,phenates, alcohol and phenol acid salts, betadiketonates and so forth.Table VIIA shows the use of barium tertiobutanolate. Examples of theGroup IIB and IIIA materials are diethylzinc, diethyl cadmium, triethylaluminum and so forth. The working examples for the preparation ofpolymers of BD and copolymers of BD and STY show η of 0.34 to 2.15,trans-1,4 of 61 to 90% and vinyl contents of 2.4 to 9%.

U.S. Pat. No. 4,092,268 is similar to U.S. Pat. No. 4,080,492 but itincludes isoprene and shows in Examples 11 and 12 the polymerization ofisoprene and the copolymerization of isoprene and styrene.

British Pat. No. 1,516,861 has a somewhat similar disclosure to that ofU.S. Pat. No. 4,080,492 and both are based on the same French patentapplication. The U.S. case apparently deleted reference to thepolymerization of isoprene.

British Pat. No. 1,525,381 (patent of addition to Br. Pat. No.1,516,861, above) discloses a process for polymerizing butadiene andcopolymerizing butadiene and styrene using a catalyst composition of (a)an organolithium, (b) a compound of barium, strontium or calcium, (c) anorganometallic compound of a metal of Group IIB or IIIA and (d) an aminoor ether alcoholate of an alkali metal. An example of (a) is n-butyllithium; of (b) is Ca, Ba or Sr alcoholate or phenate particularlybarium nonyl phenate; of (c) is (C₂ H₅)₂ Zn, (C₂ H₅)₃ Al or (i-butyl)₃Al; and of (d) is C₂ H₅ (OCH₂ CH₂)₂ OLi, (C₂ H₅)₂ NCH₂ CH₂ OLi or CH₂(OCH₂ CH₂)₂ ONa.

The working examples for the polybutadienes and butadiene-styrenecopolymers made show inherent viscosities of 0.9 to 2.4, trans-1,4contents of 80 to 90% and vinyl contents of 2 to 4%. For Example 2 it isstated that the green strength test on the black loaded uncuredcopolymers showed a similar resistance to elongation to that of naturalrubber.

A class of crystallizing elastomers based on butadiene containingsufficient amounts of the trans-1,4 structure to crystallize has beendisclosed in U.S. Pat. No. 3,992,561 (divisional U.S. patents of thesame, U.S. Pat. Nos. 4,020,115; 4,033,900 and 4,048,427 have the samedisclosure in the specification). The catalyst for the preparation ofthese polymers comprises an alkyl lithium compound such as n-butyllithium and a barium t-alkoxide salt such as a barium salt of t-butanoland water. The polymerization temperature, the nature of the solvent andthe mole ratio of the catalyst components and its concentration werefound to control the polybutadiene microstructure and molecular weight.It is stated that the crystalline melting temperature of the high transpolybutadienes can be depressed near or below room temperature by thecopolymerization of styrene, still permitting the rubber to undergostrain induced crystallization. The butadiene polymers andbutadiene-styrene copolymers exhibited green strength and tack strength.A high trans polybutadiene exhibited a broad bimodal molecular weightdistribution. This patent discloses in the working examples for theinvention polybutadiene and butadiene-styrene copolymers exhibitingintrinsic viscosities of 1.43 to 7.39, trans-1,4 contents of 63 to 80.4%and vinyl contents of 6 to 9%.

U.S. Pat. No. 4,260,712 (U.S. Pat. No. 4,260,519 is a division),discloses an improved barium t-alkoxide salt for use with a hydrocarbonlithium compound for the preparation of polybutadiene andbutadiene-styrene copolymers. It shows in the working examples forpolybutadiene and butadiene-styrene copolymers intrinsic viscosities offrom 3.74 to 7.68, trans-1,4 contents of 73 to 82% and vinyl contents of6 to 13%.

"Gummi-Asbest-Kunststoffe," pages 832 to 842, 1962 reviews severalcatalyst systems for polymerizing unsaturated monomers and discusses theproperties of several polymers. On page 835, Table 4, it discloses theuse of a catalyst system of R₂ Mg and RMgHal to polymerize butadiene tomake a polybutadiene having 45-49 trans-1,4 units.

OBJECTS

An object of the present invention is to provide a new compositionuseful as a catalyst for the solution polymerization of ethylenicallyunsaturated monomers and heterocyclic monomers.

Another object of the present invention is to provide a method forsolution polymerization of ethylenically unsaturated monomers andheterocyclic monomers using an anionic catalyst complex or composition.

These and other objects and advantages of the present invention willbecome more apparent from the following detailed description, examplesand accompanying drawings in which

FIG. 1 is a graph showing copolymer composition variation with percentconversion using different catalyst systems;

FIG. 2 is a graph showing the polybutadiene microstructure versus themole ratio of Ba[(t-RO)_(2-x) (OH)_(x) ] to (Bu)₂ Mg at Mg/Al=5.4/1(Example 1);

FIG. 3 is a graph showing the gel permeation chromatograms ofpolystyrene and polystyrene-polybutadiene diblock copolymer preparedwith the Mg-Al-Ba composition catalyst;

FIG. 4 is a graph showing the effect of chain extension on the molecularweight distribution of high trans styrene-butadiene copolymer rubber(15% styrene);

FIG. 5 is a graph showing the effect of chain extension of high transstyrene-butadiene (copolymer) rubber on variation of viscosity withshear-rate;

FIG. 6 shows x-ray diffraction patterns for a high transstyrene-butadiene rubbery copolymer (about 15% Sty; 85% Trans) of thisinvention;

FIG. 7 is a graph showing the "green-strength," stress-strain, ofuncured but compounded (45 phr of carbon black) of various rubbers;

FIG. 8 is a graph showing the effect of contact time on tack strength ofhigh trans styrene-butadiene (copolymer) rubber (15% styrene) of thisinvention and natural rubber (SMR-5), both uncured but compounded with45 phr carbon black and 13 phr oil;

FIG. 9 is a graph showing the effect of chain extension on the molecularweight distribution of a high trans polybutadiene;

FIG. 10 is a graph showing the gel permeation chromatograms of a divinylbenzene-linked poly[styrene-b-(styrene-co-butadiene)] diblock copolymerand its precursors and

FIG. 11 is a graph of a stress-strain curve of a divinyl benzene linkedstyrene-butadiene diblock polymer (40% styrene) prepared with theMg-Al-Ba catalyst of the present invention.

SUMMARY OF THE INVENTION

According to the present invention a composition of a barium alcoholateor alkoxide salt, an organoaluminum compound and an organomagnesiumcompound has been found useful as an anionic polymerization catalyst forthe solution polymerization of butadiene as well as butadiene andstyrene to make polymers having a high trans content. In place of bariumalkoxide, calcium alkoxide or strontium alkoxide can be used. Thecatalyst may be used for the polymerization of other ethylenicallyunsaturated monomers as well as heterocyclic monomers like oxiranes,thiiranes, siloxanes, thiatanes and lactams.

The homopolymer of butadiene and copolymer of butadiene with styrene ofthis invention have a high content of trans-1,4 linkages (85-90%) and alow vinyl content (2-3%) which provide sufficient amounts of trans-1,4polybutadiene placements to permit crystallization. The catalyst forthese polymerizations comprises an organomagnesium-organoaluminumcomplex, (1) [(a)alkyl₂ Mg:(b)alkyl₃ Al], where the mole ratio of (a) to(b) is from about 105/1 to 1.5/1, in combination with, (2) a barium,calcium and/or strontium (barium being preferred) salt of alcohols, oralcohols and water, the alcohol is preferably a tert-alcohol, the moleratio of barium metal to magnesium metal being from about 1/10 to 1/2.

It has been found that the trans-1,4 content of the polybutadienesegments generally is controlled by the following factors: (1) the moleratio of barium to magnesium (Ba²⁺ /Mg²⁺) present in the Mg alkyl-Alalkyl-Ba salt catalyst composition, (2) the mol ratio of Mg to Al, (3)the nature of the polymerization solvent used, (4) the polymerizationtemperature, and (5) the catalyst concentration. By the use ofappropriate polymerization variables, the trans-1,4 content issufficiently high (ca 81 to 90%) to provide a crystalline polybutadieneand for certain copolymer compositions (with styrene contents up toabout 30%) a strain-crystallizing SBR and M about 50,000 to 500,000,linear and branched.

Copolymerization of butadiene and styrene with barium t-alkoxide saltsand a complex of an organomagnesium with an organoaluminum (Mg-Al), forexample, 5.4 (n-C₄ H₉)₂ Mg. (C₂ H₅)₃ Al (MAGALA-6E, Texas Alkyls, Inc.)exhibits a higher initial rate of incorporation of styrene than a n-C₄H₉ Li catalyzed copolymerization as shown by FIG. 1.

Proton NMR analysis of these high trans SBR's (15% styrene) shows adistribution of the styrene throughout the polymer from isolated unitsto styrene sequences longer than tetrads. The amount of blockpolystyrene placements in the copolymer chain appears to rapidlyincrease as the extent of conversion increases from 90% to 100%.However, it has not been possible to isolate any polystyrene from theproducts of oxidative degradation with tert-butylhydroperoxide andosmium tetroxide [following the technique of I. M. Kolthoff, T. S. Leeand C. W. Carr, J. Polymer Sci., 1, 429 (1946)] of a high trans SBRpolymerized to 92% conversion and containing 23 weight percent (wt.%)total styrene.

One of the main factors which controls the butadiene microstructure atconstant Mg/Al ratio is the mole ratio of Ba²⁺ /Mg²⁺. This is shown byFIG. 2 for a Mg/Al ratio of 5.4/1. The trans-1,4 content ofpolybutadiene, prepared in cyclohexane at 50° C., increases and thevinyl content decreases as Ba²⁺ /Mg²⁺ decreases. Polybutadienes withtrans-1,4 contents as high as 90% with vinyl contents of 2% have beenprepared with this system at mole ratios of Ba²⁺ /Mg²⁺ of 1/5. Theoptimum Ba²⁺ /Mg²⁺ ratio is approximately 1/5.

In particular, complexes of Mg-Al with compounds of barium tert-alkoxideor barium (tert-alkoxide-hydroxide) are highly effective for thepreparation of high trans-1,4 polybutadiene (up to about 90% trans). Thebarium salts useful in the polymerization are prepared in liquidmonomethylamine or liquid ammonia by reacting barium metal with atert-alcohol or mixture of t-alcohols, or mixture of tert-alcohol(s) andwater (0.01-0.1 equivalents of the available barium is reacted withwater). Certain barium salts, such as barium(tert-decoxide-tert-butoxide-hydroxide), molar ratio oftert-decanol/tert-butanol/H₂ O (30/59/11), have the advantage that theyare soluble to greater than 20 wt.% in toluene and the solutions arestable indefinitely. Thus, they provide a soluble barium compound ofinvariant solution composition during storage.

Complexes of barium tert-butoxide (which is only sparingly soluble (0.1wt.%) in toluene at room temperature) with Mg-Al alkyls are, however,also effective catalysts for the preparation of 90% trans-1,4polybutadienes.

The polymerization activity and the amount of trans-1,4 content are verymuch dependent on the Mg/Al ratio in these Ba-Mg-Al catalysts. It hasbeen found that Mg-Al complexes containing (n-C₄ H₉)₂ Mg to (C₂ H₅)₃ Alin mole ratios of about 5.4 and 7.6 (MAGALA-6E and MAGALA-7.5E, TexasAlkyls, Inc.), respectively, are effective for preparing 90% trans-1,4polybutadiene at constant Ba/Mg=0.20. In addition, Mg-Al-Ba complexescontaining Mg and Al in ratios of 27 and 105 are capable of polymerizingbutadiene to polymers having trans-1,4 contents of about 81-83%.However, a complex of (n-C₄ H₉)₂ Mg. 2(C₂ H₅)₃ Al with Ba salts did notpolymerize butadiene.

It is possible to prepare polybutadiene with trans-1,4 contents greaterthan 85% with Ba-Mg-Al catalysts consisting of a complex of barium saltswith (sec-C₄ H₉)Mg (n-C₄ H₉) and (C₂ H₅)₃ Al, prepared in situ, in moleratios of Mg/Al ranging from about 2 to 7.6.

Alternatively, soluble catalyst compositions can be prepared by mixingclear colorless solutions of, e.g., MAGALA-6E in heptane with barium(tert-alkoxide-hydroxide) in toluene. Optionally, the catalyst can bepreformed by heating the solution for 15 minutes at 60° C. A yellowcolored solution forms upon heating, indicating complex formation (Ba²⁺/Mg²⁺ =1/5). A small amount of lightly colored precipitate is alsoformed. Active catalyst components for trans-1,4 addition are present inthe solution phase. The insoluble phase in toluene represents only asmall fraction of the total metallic compounds.

In addition to the effect of catalyst composition, the nature of thepolymerization solvent and temperature influence the microstructure ofthe butadiene based polymers. Polybutadienes prepared in paraffinic andcycloparaffinic hydrocarbon solvents have slightly higher trans-1,4contents and higher molecular weights than polymers prepared in toluene.The stereoregularity of butadiene based polymers prepared in cyclohexanewith a Mg-Al-Ba catalyst is dependent on polymerization temperature. Thedecrease in trans-1,4 content with increasing polymerization temperatureoccurred with a corresponding increase in both vinyl and cis-1,4contents.

The concentration of catalyst affects both the trans-1,4 content andmolecular weight of polybutadiene prepared in cyclohexane at 50° C. Thetrans-1,4 content increases non-linearly with a decrease in the molarratio of the initial butadiene to (n-C₄ H₉)₂ Mg concentration, at aconstant Ba/Mg ratio. The trans-1,4 content appears to reach a limitingvalue of about 90% for polybutadienes prepared with relatively largeamounts of catalyst.

Molecular weight increases with an increase in the molar ratio ofbutadiene to (n-C₄ H₉)₂ Mg as well as with an increase in the extent ofconversion. In addition, the viscosity of a solution of non-terminatedpolybutadienyl anion increases with the addition of more monomer. Theabove results demonstrate that a certain fraction of the polymer chainends retain their capacity to add monomer.

The crystalline melting temperatures (45° C., 70° C.) of thesepolybutadienes can be decreased to near or below room temperature (about25° C.) by adjustments of the trans-1,4 content and the incorporation ofa comonomer (styrene). The resultant copolymers are then amorphous atroom temperature but will undergo strain-induced crystallization. Therubbers are characterized by both green strength and tack strength equalto or higher than natural rubber. As such, these synthetic rubbers canbe expected to be of value in those applications where natural rubber isused. One of these applications is as a tire rubber, especially inradial ply tire construction. In addition, the ability to control themolecular structure of these rubbers makes them useful materials in tiretread compounds.

For styrene-butadiene copolymers, prepared with Mg-Al-Ba catalysts atBa/Mg of 0.20 to 0.25, the molecular weight appears to be controlled byboth the level of Mg and Ba used in the polymerization. The molecularweight of high trans polybutadiene and polystyrene as well as STY-BDcopolymers increases with an increase in initial molar concentrations ofmonomer(s)/Mg at constant Ba/Mg.

Discussion of Details and Preferred Embodiments

The barium (preferred), calcium or strontium alcoholate or alkoxide saltor mixture of such salt is made by reacting an alcohol, preferably atertiary alcohol or mixture of tertiary alcohols, optionallyadditionally including water, with Ba, Ca and/or Sr. It is better toconduct the reaction in liquid NH₃ or amine solvent at a temperature offrom about -100° C. up to the boiling point of the solvent or above theboiling point under pressure. After the reaction, the NH₃ or amine canbe removed from the salt by distillation, vacuum evaporation and solventextraction. Preferably, the salt is dried in a vacuum at reducedpressure for a period of time sufficient to reduce the nitrogen contentof the salt to not greater than about 0.1, preferably not greater thanabout 0.01%, by weight. Methods of making the barium alkoxide salts,such as barium t-alkoxide salts, which also will be applicable to thecorresponding Ca and Sr salts, are shown in U.S. Pat. No. 3,992,561 andU.S. Pat. No. 4,260,712 (U.S. Pat. No. 4,260,519 is a division), thedisclosures of which are incorporated herein and made a part hereof byreference to the same.

Examples of alcohols to use to make the Ba, Ca and/or Sr salts oralcoholates are methanol, ethanol, propanol, isopropanol, n-butanol,cyclopentanol, cycloheptanol, cyclohexanol, s-butanol, t-butanol,pentanol, hexanol, octanol, and decanol and so forth and mixtures of thesame. Examples of such alcoholates are calcium diethoxide, di(t-butoxy)strontium, di(isopropoxy) barium, di(cyclohexyloxy) barium and so forth.If a non-tertiary alcohol or carbinol is used, it is preferred that themixture contain at least 50 mol % of a tertiary carbinol.

The preferred carbinol to use is a tertiary carbinol, having the generalformula ##STR1## where the Rs are selected from the group consisting ofalkyl or cycloalkyl radicals of from 1 to 6 carbon atoms which may bethe same or different such as a methyl, ethyl, propyl, butyl, isopropyl,amyl, cyclohexyl and the like radicals. Examples of these tertiarycarbinols are t-butanol, 3-methyl-3-pentanol, 2-methyl-2-butanol,2-methyl-2-pentanol, 3-methyl-3-hexanol, 3,7-dimethyl-3-octanol,2-methyl-2-heptanol, 3-methyl-3-heptanol, 2,4-dimethyl-2-pentanol,2,4,4-trimethyl-2-pentanol, 2-methyl-2-octanol, tricyclohexyl carbinol,dicyclohexyl propyl carbinol, cyclohexyl dimethyl carbinol, t-decanol(4-n-propyl-heptanol-4), 3-ethyl-3-pentanol, 3-ethyl-3-hexanol,3-ethyl-3-heptanol, 3-ethyl-3-octanol, 5-ethyl-5-nonanol,5-ethyl-5-decanol, 6-ethyl-6-undecanol, 5-butyl-5-nonanol,4-isopropyl-4-heptanol, 2-methyl-4-n-propyl-4-heptanol,4-n-propyl-4-nonanol, 5-n-propyl-5-nonanol,2,2-dimethyl-4-n-propyl-4-heptanol, 4-n-propyl-4-decanol,5-n-propyl-5-decanol, 2,6-dimethyl-4-isobutyl-4-heptanol,3,3,6-trimethyl-4-n-propyl-4-heptanol, 6-n-propyl-6-undecanol,5-n-butyl-5-decanol, 6-n-butyl-6-undecanol, 6-n-pentyl-6-undecanol,2,8-dimethyl-5-isopentyl-5-nonanol, and2,8-dimethyl-5-isobutyl-5-nonanol and the like and mixtures of the same.

There, also, may be used a tertiary carbinol having the general formula##STR2## where R' is an alkyl radical of from 1 to 4 carbon atoms whichmay be the same or different and where R" is a hydrocarbon radicalhaving a molecular weight of from about 250 to 5,000. These materialsmay be obtained by polymerizing in solvent media butadiene and/orisoprene with or without a minor amount of styrene and/or alpha methylstyrene using a monolithium hydrocarbon catalyst such as butyllithium toobain a liquid lithium terminated polymer or oligomer. The preparationof such liquid diene containing polymers is known. See U.S. Pat. No.3,078,254. Appreciable amounts of catalyst are used to obtain liquidpolymers. See U.S. Pat. No. 3,301,840. The resulting polymer solution isthen treated with an epoxide such as isobutylene oxide ##STR3## toobtain a product which may be shown as: ##STR4## In place of isobutyleneoxide there can be used 1,1-diethyl-1,2-epoxyethane,1,1-dipropyl-1,2-epoxyethane, 1,1-diisopropyl-1,2-epoxyethane,1,1-dibutyl-1,2-epoxyethane, 1,1-diisobutyl-1,2-epoxyethane and the likeepoxide and mixture thereof. See U.S. Pat. No. 3,538,043. These epoxidetreated lithium terminated polymers can then be hydrolyzed with water toform the tertiary carbinol or alcohol: ##STR5## The hydrolyzed polymeror liquid tertiary carbinol is then removed from the organic solvent andis ready for reaction with barium to form a barium tertiary alkoxidesalt.

Mixtures of the above tertiary carbinols can be used.

Water, if used in preparing the Ba, Ca or Sr alcoholates or salts, isemployed in the alcohol or alcohol mixture as follows:

from about 0 to 20, preferably from about 0 to 12, mol% of water to fromabout 100 to 80, preferably from about 100 to 88, mol% of the alcohol oralcohol mixture.

The resulting preferred alcoholate or alkoxide salt, or mixture of saidsalts, preferably containing not over about 0.1%, and even morepreferably not over about 0.01% by weight of nitrogen, have thefollowing general formulae: ##STR6## where the mol ratio of a to b isfrom about 100:0 to 80:20, preferably from about 100:0 to 88:12, andwhere R, R' and R" are the same as defined above and where M is barium,calcium and/or strontium, preferably barium, or mixture of said metalsalts or alcoholates.

The organoaluminum compounds used in the practice of the presentinvention are alkyl and cycloalkylaluminum compounds. These compoundscan be prepared by reacting aluminum metal with an olefin in thepresence of hydrogen. Another method, for example, comprises thereaction:

    2Al+3(CH.sub.3).sub.2 Hg→3Hg+2(CH.sub.3).sub.3 Al.

Other methods can be used. See "Aluminum Alkyls," Texas Alkyls,Copyright 1976 by Stauffer Chemical Company, Westport, Conn., 71 pagesincluding the bibliography shown therein and "Encyclopedia of PolymerScience and Technology," Vol. 1, 1964, Interscience Publishers adivision of John Wiley & Sons, Inc., New York, Pages 807 to 822. Theseorganoaluminum compounds have the general formula R₃ ^(III) Al whereR^(III) is an alkyl radical or cycloalkyl radical, which may be the sameor different, of from 1 to 20, preferably of from 1 to 10, carbon atoms.Mixtures of these organoaluminum compounds can be used. Examples of suchcompounds are trimethyl aluminum, triethyl aluminum, tri-n-propylaluminum, triisopropyl aluminum, pentyl diethyl aluminum,2-methylpentyl-diethyl aluminum, tri-n-butyl aluminum, triisobutylaluminum, dicyclohexylethyl aluminum, tri-n-pentyl aluminum, tri-n-hexylaluminum, tri-n-octyl aluminum, tri(2-ethylhexyl)aluminum,tricyclopentyl aluminum, tricyclohexyl aluminum,tri(2,2,4-trimethylpentyl)aluminum, tri-n-dodecyl aluminum, andtri(2-methylpentyl)aluminum and the like.

The organomagnesium compounds used in the practice of the presentinvention are alkyl and cycloalkyl magnesium compounds. These compoundscan be prepared by the action of R₂ Hg on magnesium, the reaction beingfacilitated by the presence of ether. They, also, may be prepared byallowing olefins to react under pressure at about 100° C. with magnesiummetal in the presence of hydrogen. Please see "OrganometallicCompounds," Coates et al, Vol. 1, 1967, 3rd Ed., Methuen & Co. Ltd.,London. These organomagnesium compounds have the general formula R₂^(IV) Mg where R^(IV) is an alkyl radical or cycloalkyl radical, whichmay be the same or different, of from 1 to 20, preferably of from 1 to10, carbon atoms. Mixtures of these organomagnesium compounds can beused. Examples of such compounds are dimethyl magnesium, diethylmagnesium, dipropyl magnesium, di-n-butyl magnesium, di-sec-butylmagnesium, di-n-amyl magnesium, methylethyl magnesium, n-butyl ethylmagnesium (BEM), n-propylethyl magnesium, di-n-hexyl magnesium,dicyclohexyl magnesium, cyclohexylethyl magnesium, didecyl magnesium,di-ter-butyl magnesium and didodecyl magnesium and the like.

Organo Mg-Al complexes can be used instead of mixtures of Mg and Alcompounds. One method of preparation is to add the organoaluminumcompound to a reactor containing the reaction products of organichalides with magnesium in hydrocarbon solvent. After filtration of thereaction mixture, there is obtained a solution of the complex containinglittle soluble halides. Please see Malpass et al, "Journal ofOrganometallic Chemistry," 93 (1975), Pages 1 to 8. These complexes willhave the general formula R_(m) ^(III) Al_(n).R_(p) ^(IV) Mg_(q) wherethe mol ratio of Al to Mg is as set forth herein, where m, n, p and qare numbers sufficient to satisfy the required valences of the radicalsand atoms and where R^(III) and R^(IV) are alkyl or cycloalkyl radicals,which may be same or different, as described above.

In the catalyst composition the mol ratio computed as metal of magnesiumto aluminum is from about 105:1 to 1.5:1, and the mol ratio computed asmetal of barium, calcium and/or strontium to magnesium is from about1:10 to 1:2.

Just prior to polymerization, the barium salt, the organoaluminumcompound and the organomagnesium compound (or theorganoaluminum.magnesium complex) each in hydrocarbon solution are mixedtogether. The time required to form a catalyst complex or compositionranges from a few minutes to an hour or longer depending on the reactiontemperature. This should be accomplished under an inert atmosphere, andthe ingredients may be heated to speed reaction at temperatures of fromabout 25° to 100° C., preferably from about 40° to 60° C. After thecatalyst composition has formed, the polymerization solvent andmonomer(s) may be charged to the catalyst, or the preformed catalystdissolved in its solvent may be injected into a reactor containing themonomers dissolved in the hydrocarbon polymerization solvent.

The monomers to be polymerized can be ethylenically unsaturated monomersor heterocyclic monomers. The ethylenically unsaturated polymerizablemonomers to be polymerized with the catalysts of the present inventionare those having an activated unsaturated double bond, for example,those monomers where adjacent to the double bond there is a group moreelectrophilic than hydrogen and which is not easily removed by a strongbase. Examples of such monomers are nitriles like acrylonitrile andmethacrylonitrile; acrylates and alkacrylates like methyl acrylate,ethyl acrylate, butyl acrylate, ethyl hexyl acrylate, octyl acrylate,methyl methacrylate, ethyl methacrylate, butyl methacrylate, methylethacrylate, ethyl ethacrylate, butyl ethacrylate and octyl ethacrylate;the dienes such as butadiene-1,3 and isoprene; and the vinyl benzeneslike styrene, alpha methyl styrene, p-tertiary butyl styrene, divinylbenzene, methyl vinyl toluene and para vinyl toluene and the like andmixtures of the same. Examples of polymerizable heterocyclic monomersare oxiranes like ethylene oxide, propylene oxide, 1,2-butylene oxide,styrene oxide, isobutylene oxide, allyl glycidyl ether, phenyl glycidylether, crotyl glycidyl ether, isoprene monoxide, butadiene monoxide,vinyl cyclohexane monoxide and the like and mixtures thereof. Otherheterocyclic monomers which may be polymerized are siloxanes such asoctamethyl tetrasiloxane, thiiranes like propylene sulfide, thiataneslike thiacyclobutane and lactams like epsilon-caprolactam. Depending onthe monomer employed, the resulting polymers can be rubbery, resinous,or thermoplastic. For example, a homopolybutadiene prepared according tothe present invention having 90% trans content is thermoplastic orresinous, while a copolymer of butadiene and styrene containing about15-20% styrene and 90% trans is still rubbery.

Preferred monomers for use in the practice of the present invention aremixtures of butadiene-1,3 and up to about 30% by weight total of themixtures of styrene to make rubbery copolymers exhibiting a hightrans-1,4 content and a low vinyl content. Moreover, by altering thebutadiene-styrene copolymer composition or microstructure a rubber canbe prepared which has behavior closely simulating that of natural rubberin building tack and green strength. Thus, it is within the scope ofthis invention to prepare polymers which can serve as replacements inthose applications where natural rubber is employed such as in tires.

The obtained number-average molecular weight in the absence of chaintransfer is controlled by the molecular weight calculated from the ratioof grams of monomer polymerized to moles of catalyst charged.Conversions of monomer to polymer up to about 100% may be obtained.

Temperatures during solution polymerization can vary from about 0° to150° C. Preferably, polymerization temperatures are from about 30° to100° C. Time for polymerization will be dependent on the temperature,amount of catalyst, type of polymers desired and so forth. Only minoramounts of the catalyst composition are necessary to effectpolymerization. However, the amount of catalyst employed may vary withthe type of polymer desired. For example, in general, when makingpolymers having a high average molecular weight using a given amount ofmonomer, only a small amount of the catalyst complex is necessarywhereas when making a low average molecular weight polymer, largeramounts of the catalyst complex are employed. Moreover, since thepolymer is a living polymer, it will continue to grow as long as monomeris fed to the polymerization system. Thus, the molecular weight can beas high as a million or even more. On the other hand, very highmolecular weight polymers require lengthy polymerization times for agiven amount of the catalyst complex, and at lower catalyst complexconcentrations the polymerization rate will drop. A useful range ofcatalyst complex to obtain readily processable polymers in practicabletimes is from about 0.00001 to 0.10, preferably from about 0.00033 to0.005, mol of the catalyst complex or composition computed as magnesiumper 100 grams total of monomer(s).

Since the polymer in solution in the polymerization media is a livingpolymer or since the polymerization is a non-terminating polymerization(unless positively terminated by failure to add monomer or by adding aterminating agent such as methanol), block polymers can be prepared bysequential addition of monomers or functional groups can be added. Also,since the living polymer contains a terminal metal ion, it as shownabove can be treated with an epoxide like ethylene oxide and then withwater to provide a polymer with a terminal hydroxyl group for reactionwith a polyisocyanate to jump the polymer through formation ofpolyurethane linkages.

The polymerization is conducted in a liquid hydrocarbon solvent. Whilebulk polymerization may be used, such presents heat transfer problemswhich should be avoided. In solvent polymerizations it is preferred tooperate on a basis of not over about 15 to 20% polymer solidsconcentration in the solvent to enable ready heat transfer andprocessing. Solvents for the monomers and polymers should not have avery labile carbon-hydrogen bond and should not act at leastsubstantially as chain terminating agents. They preferably should beliquid at room temperature (about 25° C.). Examples of such solvents arebenzene (less desirable), toluene, the xylenes, the trimethyl benzenes,hemimellitene, pseudocumene, mesitylene, prehnitene, isodurene, o, m,and p cymenes, ethylbenzene, n-propylbenzene, cumene, 1,2,4- or1,3,5-triethylbenzene, n-butyl benzene and other lower alkyl substitutedbenzenes, hexane, heptane, octane, nonane, cyclohexane, cycloheptane,cyclooctane and the like and mixtures of the same. The saturatedaliphatic and cycloaliphatic solvents and mixtures thereof arepreferred. Some solvents may give lower trans contents but on the otherhand may give higher molecular weights.

Polymerization, of course, should be conducted in a closed reactor,preferably a pressure reactor, fitted with a stirrer, heating andcooling means, with means to flush with or pump in an inert gas such asnitrogen, neon, argon and so forth in order to polymerize under inert ornon-reactive conditions, with means to charge monomer, solvent andcatalyst, venting means and with means to recover the resulting polymerand so forth.

The rate of polymerization can be increased by the addition of small(catalytic) amounts of ethers, amines or water. For example, theaddition of anisole to the Mg-Al-Ba catalyst system increased the rateof copolymerization of butadiene with styrene in cyclohexane at 50° C.without affecting the percent trans-1,4 content and the rate ofincorporation of styrene. Anisole appears to be more effective forincreasing the rate of polymerization than triethylamine but lesseffective than tetrahydrofuran (THF). However, a polybutadiene preparedin the presence of THF had a microstructure of 75% trans and 6% vinyl.

A small amount (catalytic) of free water, oxygen or ammonia, also, seemsto be beneficial in the preparation of polymers with the Ba-Al-Mginitiator system. The addition of a small amount of either of thesematerials increases the polymerization rate and the molecular weight ofpolymers prepared with this novel initiator system. When the free wateris added in small amounts, the trans-1,4 content of the polybutadiene orbutadiene-1,3/styrene copolymer is not affected if the mole ratio of theBa salt to the organomagnesium compound is kept at Ba/Mg=0.20.

The rate of polymerization can also be increased by increasing theinitial molar concentrations of monomers like butadiene and the Mg-Al-Bacatalyst composition.

Since the polymers produced by the method of the present inventioncontain active sites or are living polymers, they can be chain extendedor branched at any practical time prior to termination or short stoppingthe polymerization reaction. This may be obtained by adding to thepolymerization reaction media chain extenders or branching compoundssuch as dibromomethane, 1,2-dibromoethane, silicon tetrachloride andhexachlorosilane. Other chain extenders that may be used include divinyland trivinyl aromatic compounds like divinyl benzene (1,2; 1,3 or 1,4),1,3 divinyl naphthalene, 1,2,4-trivinyl benzene, vinyl silanes (such asdi, tri and tetravinyl silanes) and so forth; diisocyanates andpolyisocyanates like 1,6-diisocyanate hexane (may be carcinogenic),diphenylmethane diisocyanate and so forth (isocyanates like tolylenediisocyanate and tetramethylene diisocyanate may be unsatisfactory);diepoxides like cyclohexane diepoxide, 1,4-pentane diepoxide and soforth; polyepoxides having more than 2 epoxide groups like a phenolicnovolak epoxide or a tetra phenylolethane epoxide; diketones like2,4-hexane-di-one, 2,5-hexane-di-one and so forth and dialdehydes like1,4-butanediol, 1,5-pentanedial and so forth (see U.S. Pat. No.3,985,830). The chain extender should be soluble in the polymerizationmedia such as the solvent. Moreover, the chain extender should not killthe carbanions, or if it does, there should be sufficient carbanionspresent so that the chain extension proceeds in a satisfactory mannerbefore the chain extension reaction ceases. The chain extender can beused in an amount of from about 0.01 to 10.0 parts by weight per 100parts by weight total of the monomers initially charged. For example,butadiene or mixtures of at least 50% by weight of butadiene and thebalance essentially styrene can be polymerized to about 85% by weightconversion to provide homopolymers or block or random copolymers usingthe catalyst composition of the present invention and then can bereacted with one of the branching or chain extending compounds such asmentioned above to obtain extended, branched or star polymers. Compoundssuch as chlorosilanes, esters of poly carboxylic acids such as thetriethyl ester of trimellitic acid and the like terminate thepolymerization reaction. On the other hand compounds like divinylbenzene (preferred), trivinyl benzene, divinyl naphthalene, divinylsilane, trivinyl silane, tetravinyl silane, the organic diisocyanatesand the epoxides having more than two epoxide groups can providenon-terminating extended, branched or star polymers which still containanionic sites in the center of the molecule which are capable ofreacting and/or initiating polymerization of polar cyclic or vinylmonomers. Thus, these non-terminating polymers, such as star polymers,then can be reacted or polymerized further with copolymerizable polarmaterials like the acrylates (ethyl acrylate, butyl acrylate and thelike), the alkacrylates (methyl methacrylate (preferred),ethylmethacrylate and so forth), the nitriles (like acrylonitrile,methacrylonitrile and so forth), the epoxides (like ethyleneoxide,propyleneoxide and so forth), the siloxanes (like octomethyltetrasiloxane and the like), and the lactones (likeepsilon-caprolactone) to provide star based butadiene orbutadiene-styrene copolymers having different characteristics due to theadded polar material such that they may become more compatible withresins like polystyrene, polymethylmethacrylate, FRPs (thermosettingpolyester-styrene-glass fiber compositions) and so forth as impactmodifiers and low profile or low shrink additives. The polar materialmay be polymerized onto the star polymer in an amount of up to about 30parts by weight of the polar material per 100 parts by weight of thestar polymer. Further addition of catalyst during the branching andaddition reactions or polymerizations is generally not required sincethe original polymer and star polymer (if not terminated) contain activesites for further addition or polymerization. A feature of this aspectof the present invention is that one can obtain star polymers with ahigh trans content and the ability to crystallize and further, ifdesired, with compatibilizing groups like acrylate groups, nitrilegroups and so forth.

After polymerization the catalyst may be terminated by adding water,alcohol or other agent to the polymeric solution. After the polymer hasbeen recovered and dried, a suitable antioxidant such as2,6-di-tert-butyl-p-cresol or other antioxidant may be added to thesame. However, the antioxidant may be added to the polymeric solutionbefore it is stripped of solvent.

The polymers produced by the method of the present invention can becompounded and cured in the same manner as other plastic and rubberypolymers. For example, they can be mixed with sulfur or sulfurfurnishing materials, peroxides, carbon black, SiO₂, TiO₂, Sb₂ O₃, rediron oxide, other rubber fillers and pigments, tetramethyl or ethylthiuram disulfide, benzothiazyl disulfide and rubber extending orprocessing mineral or petroleum oils and the like. Stabilizers,antioxidants, UV light absorbers and other antidegradants can be addedto these polymers. They can also be blended with other polymers likenatural rubber, butyl rubber, butadiene-styrene-acrylonitrileterpolymers, polychloroprene, SBR, polyurethane elastomers and so forth.

The polymers produced by the method of the present invention can be usedin making protective coatings for fabrics; body and engine mounts forautomobiles; gaskets; sidewalls, treads and carcasses for tires; belts;hose; shoe soles; and electric wire and cable insulation; and asplasticizers and polymeric fillers for other plastics and rubbers. Withlarge amounts of sulfur hard rubber products can be made.

The following examples will serve to illustrate the present inventionwith more particularity to those skilled in the art. Parts are parts byweight unless otherwise stated.

The polymerizations described in the examples were carried out in anargon atmosphere in capped glass bottles fitted with neoprene rubbergasket inner liners. Solvents were purified by passing the liquidthrough columns of 5 Å molecular sieves. Butadiene (99 mol %) waspurchased from Phillips Petroleum Company. Purification was accomplishedby passing the BD through columns of 13X molecular sieves. Isoprene waspurchased from Phillips Petroleum (99.5 mol % pure) and was furtherpurified by distillation from sodium ribbon. Styrene was purchased fromGulf Oil Chemical and El Paso Products, Texas, and vacuum distilled froma small quantity of (n-butyl) (sec-butyl) magnesium. Propylene oxide wasused as received from Oxirane Corporation (contained 75 parts of waterper million).

In charging the polymerizations, the order of addition of materials wassolvent first, then Mg-Al alkyls, next the barium salt, and finally themonomer(s). The copolymer composition and percent polybutadienemicrostructure were obtained from infrared analysis, unless otherwisenoted, and from ¹³ C NMR (Nuclear Magnetic Resonance) for certainpolymers. The microstructure values determined from IR and ¹³ C NMR wereessentially identical. The trans-1,4 and vinyl content were determinedusing the 967 cm⁻¹ and 905 cm⁻¹ infrared absorption bands, respectively.Intrinsic viscosities were determined in toluene at 25° C. Gelpermeation chromatograms (GPC) were obtained using a Waters GelPermeation Chromatograph. Solutions at 1 wt.% were injected onto columnsat a flow rate of 1 ml/minute. The instrument oven and the differentialrefractometer were at 50° C. The column set configuration used, asdesignated by Waters Associates, was 1×10⁶ Å+1×10⁵ Å+1×10⁴ Å+1×10³ Å.

All thermal transitions were obtained by Differential Thermal Analysis(DTA) using a heating rate of 20° C./minute. Crystalline meltingtemperatures were determined from the position of the endothermicpeak(s) present in the curve, obtained after cooling the sample from125° C. to -150° C. at approximately 20° C./minute.

X-ray diffraction patterns were obtained from films cured with 1%dicumyl peroxide in the absence of fillers. All the experiments werecarried out at room temperature using CuKα radiation and a nickelfilter.

EXAMPLE 1 (a) Barium Salt

To 82.2 milliequivalents (meq) of barium metal (5.65 g) was added 325 mlof monomethylamine which had been flash distilled from Na-dispersion.The reactor was cooled to -78° C. with rapid stirring and a deep bluecolored solution, characteristic of the amine solution of the metal, wasobtained. To this solution a mixture of t-decanol (21 milliequivalents),t-butanol (40 milliequivalents) and water (7.3 milliequivalents) inbenzene (3.75 mols total t-alcohols in benzene) was slowly added and thereaction mixture was stirred for 3 hours and then allowed to stand for 2days at -15° C., which resulted in the quantitative conversion of thealcohols and water to barium salts. After flash distillation of theamine, the resulting white solid (11.28 g) was dried at 100° C. undervacuum. Toluene (475 g) was added to the salts and the reactor washeated to 70° C. for 2 hours. The total alkalinity of a hydrolyzedaliquot of the clear colorless solution, removed from the excess bariummetal, measured 0.148 meq of hydroxide per gram or 2.4 wt.% bariumsalts, demonstrating total dissolution of the salt. The empiricalcomposition of this product can be represented as:

    Ba[(t-C.sub.4 H.sub.9 O).sub.1.17 (t-C.sub.10 H.sub.21 O).sub.0.61 (OH).sub.0.22 ].

(b) Barium-Mg-Al Catalyst Complex Composition

Solutions of (1) [5.4 (n-C₄ H₉)₂ Mg.(C₂ H₅)₃ Al] complex (MAGALA-6E) and(2) barium salts, prepared according to Example 1 (a) above, werecharged to the polymerization solvent under an inert atmosphere. Priorto addition of monomer(s), the catalyst mixture was permitted to reactinitially at 60° C. for 15 minutes. The mole ratio of barium tomagnesium was based on the moles of total alkalinity of the solublebarium salts (one-half the milliequivalents of titratable base) to themoles of magnesium is MAGALA-6E. MAGALA-6E was obtained from TexasAlkyls (25 wt.% in heptane) and diluted with cyclohexane to aconcentration of 0.28 meq of magnesium (0.075 meq aluminum) per gram ofsolution. The magnesium and aluminum contents were determined by atomicabsorption spectroscopy, and the molar ratio of Mg/Al was found to be5.4/1 for a complex designated by Texas Alkyls, Inc., as MAGALA-6E

    (5.4[(n-C.sub.4 H.sub.9).sub.2 Mg].[C.sub.2 H.sub.5).sub.3 Al]).

EXAMPLE 2

This example demonstrates the usefulness of the catalyst, described inExample 1, for the preparation of crystalline butadiene based polymers.Table I, below, shows that polybutadienes of this invention have a highdegree of stereoregularity with crystalline melting temperatures of 43°C. and 70° C. The high trans-1,4 configuration (89%) results in athermoplastic polymer which is hard and highly crystalline at roomtemperature.

Isoprene can be polymerized with a Mg-Al-Ba catalyst composition, asdescribed in Table I. A polyisoprene was obtained with an isomer contentof 49% trans, 39% cis and 12% 3,4.

                  TABLE I                                                         ______________________________________                                        Molecular Structure of Polydiene and                                          Styrene-Butadiene Copolymer                                                   Prepared in Cyclohexane at 50° C.                                      with Mg--Al--Ba Catalyst Composition                                          (Mg/Al = 5.4/1, Ba/Mg = 1/5, mol ratios of metal)                             ______________________________________                                                        g. Total                                                                      Monomers  %                                                   Run  Monomer(s) per mM    Conversion                                                                            Wt. % Styrene                               No.  (grams)    (Bu).sub.2 Mg                                                                           (hours)                                                                              Charged Found                                ______________________________________                                        1    Butadiene  38.7      100 (91)                                                                             --      --                                        (27.1)                                                                   2    Butadiene/ 45.5      86 (118)                                                                             22      17                                        Styrene                                                                       (24.4/7.0)                                                               3    Isoprene   34.1      98 (77)                                                                              --      --                                        (23.9)                                                                   ______________________________________                                                                       Peak                                                                   tol    Crystalline                                    Run     % Diene Structure                                                                             [η]25                                                                            Melting Temp.                                  No.     Trans-1,4                                                                              Vinyl      dl/g (°C.)                                 ______________________________________                                        1       89.sup.  2.sup.     2.11 43, 70                                       2       88.sup.a 2.sup.a    1.60 19                                           3       49.sup.a (12).sup.a,b                                                                             0.92 None observed.                               ______________________________________                                         .sup.a percent microstructure determined by .sup.13 C NMR                     .sup. b value in parenthesis represents 3,4 content                      

The rate of polymerization is faster for butadiene polymers than forbutadiene-styrene copolymers. For example, complete conversion ofbutadiene to polymer is readily obtained in 24 hours at 65° C. Withbutadiene-styrene copolymers, it is difficult to obtain a conversion inexcess of 90% in 24 hours at 65° C. Further, the remaining 10% monomerin the SBR system is primarily styrene, and it requires in excess of 72hours at 65° C. to obtain complete conversion. Viscosities (η) areintrinsic viscosities in deciliters per gram in toluene at 25° C.

EXAMPLE 3

A polystyrene-polybutadiene diblock copolymer (41% styrene) was preparedwith the Mg-Al-Ba catalyst composition (described in Example 1) by theaddition of butadiene to a non-terminated solution of polystyrylcarbanions. Styrene was polymerized to 96% conversion, see Table II,below, and the resulting polystyryl carbanion was used in Run 5. Allpolymerizations were conducted in cyclohexane at 50° C.

                                      TABLE II                                    __________________________________________________________________________    Preparation of Polystyrene-Polybutadiene Diblock Copolyer                     and Hydroxyl Terminated Polybutadiene with Mg--Al--Ba Catalyst                          g. Total                                                                      Monomers                                                                             %             --M.sub.n                                                                         tol                                        Run                                                                              Monomers(s)                                                                          per mM Conversion                                                                           Wt. %  ×                                                                           [η]25                                  No.                                                                              (grams)                                                                              (Bu).sub.2 Mg                                                                        (hours)                                                                              Composition                                                                          10.sup.-3d                                                                        dl/g.sup.d                                 __________________________________________________________________________    4  Styrene.sup.a                                                                        15.9   96.sup.a (48)                                                                        % styrene                                                                            20.sup.c                                                                          0.20                                          (10.5)               = 100                                                 5  Polystyryl    1. 96 (48)                                                      (10.5)                                                                        Butadiene                                                                            39.1   2. 98 (119)                                                                          % styrene                                                                            114.sup.c                                                                         0.93                                          (14.8)               = 41                                                  6  Butadiene                                                                            23.5   88 (115)                                                        (24.2)                                                                        Ethylene             % hydroxyl                                                                           51.sup.b                                                                          1.31                                          Oxide                = 0.031                                                  (0.09)                                                                     __________________________________________________________________________     .sup.a polystyrene precursor used in the preparation of                       polystyrenepolybutadiene diblock copolymer (Run 5).                           .sup.b --M.sub.n measured by membrane osmometry.                              .sup.c --M.sub.n estimated by GPC.                                            .sup. d final polymer.                                                   

FIG. 3 shows two MWD (Molecular Weight Distribution) curves of thisdiblock copolymer (Run 5) and its polystyrene precursor (Run 4). Acomparison of the peak positions in the MWD curves and the shapes of thecurves demonstrates the successful preparation of a diblock copolymer.Homopolymers of styrene or butadiene could not be extracted from thereaction products using acetone/cyclohexane (75/25) and n-pentane assolvents for polystyrene and polybutadiene, respectively, and asnonsolvents for the diblock copolymer.

A hydroxyl terminated polybutadiene (Run 6) was prepared by the additionof ethylene oxide at the end of a butadiene polymerization initiatedwith Mg-Al-Ba catalyst (see Table II). The terminal alkoxide units werethen hydrolyzed to form the carbinol. The hydroxyl functionality of thispolymer was 0.91 based on hydroxyl equivalent molecular weight andnumber-average molecular weight.

These results demonstrate that polybutadiene or polystyrene chain endsretain their capacity to add monomer and can be derivatized to result inuseful materials. Thus, block copolymers, functionally terminatedpolymers and polymers with different molecular architecture andmolecular weight distribution can be prepared.

EXAMPLE 4

Polymerizations of butadiene were carried out according to Run 1,Example 2 using various Ba and Ca compounds substituted forbarium(t-decoxide-t-butoxide-hydroxide), designated as the control. Theresults are given in Table III, below. Ba salts of t-butanol andmixtures of t-butanol and water, both prepared according to Example 1,were equally effective as the control for the preparation of about 90%trans-1,4 polybutadiene. Barium ethoxide complexed with Mg-Al alkylspolymerized butadiene to a high molecular weight polymer having a dienestructure of 76% trans-1,4 and 7% vinyl. Complexes of Mg-Al alkyls withCa[(t-C₄ H₉ O)₁.8 (OH)₀.2 ] are catalysts for the quantitativepolymerization of butadiene (see Runs 10-13, Table III). However, themaximum in trans-1,4 content of 77% occurred for a Ca²⁺ /Mg²⁺ ratio of0.51 in comparison to a trans-1,4 of up to 90% for a Ba²⁺ /Mg²⁺ ratio of0.20. This example demonstrates the usefulness of certain Ba and Caalkoxide salts in preparing high trans-1,4 crystallizing polybutadiene.

                  TABLE III                                                       ______________________________________                                        Effect of Composition of Various Ba and Ca Compounds                          on the Molecular Structure of Polybutadiene.sup.a                             ______________________________________                                                                           %                                                 Composition of  Mole Ratio  Conversion                                 Run No.                                                                              Group IIA Salt  Me.sup.2+ /Mg.sup.2+                                                                      (hours)                                    ______________________________________                                         1     Ba[(t-C.sub.10 H.sub.21 O).sub.0.61                                                           0.20        100 (91)                                          (t-C.sub.4 H.sub.9 O).sub.1.17 (OH).sub.0.22 ]                                (CONTROL)                                                               7     Ba[(t-C.sub.4 H.sub.9 O).sub.1.8 (OH).sub.0.2 ]                                               0.20        90 (43)                                     8     Ba (t-C.sub.4 H.sub.9 O).sub.2                                                                0.20        96 (71)                                     9     Ba (C.sub.2 H.sub.5 O).sub.2                                                                  0.18         82 (168)                                  10     Ca[(t-C.sub.4 H.sub.9 O).sub.1.8 (OH).sub.0.2 ]                                               0.11        99 (47)                                    11     Ca[(t-C.sub.4 H.sub.9 O).sub.1.8 (OH).sub.0.2 ]                                               0.25        98 (71)                                    12     Ca[(t-C.sub.4 H.sub.9 O).sub.1.8 (OH).sub.0.2 ]                                               0.51        97 (24)                                    13     Ca[(t-C.sub.4 H.sub.9 O).sub.1.8 (OH).sub.0.2 ]                                               0.90        100 (72)                                     13-1 Ba[t-C.sub.10 H.sub.21 O).sub.1.8 (OH).sub.0.2 ]                                              0.20        100 (70)                                   ______________________________________                                                %           Crystalline                                                                             tol                                                      Diene Structure                                                                          Melting   [η]25                                       Run No.   Trans   Vinyl     Temp., °C.                                                                     dl/g                                      ______________________________________                                         1        89      2         43, 70  2.11                                       7        90      3         29, 59  1.38                                       8        88      2         41, 68  2.92                                       9        76      7           9     1.68                                      10        64      8         -30     Soft                                                                          Polymer                                   11        70      7         -11     Soft                                                                          Polymer                                   12        77      6         11, 27  0.90                                      13        72      6          -2     1.36                                        13-1    86      3         38, 58  Rubber                                    ______________________________________                                         .sup.a polymerization solvent: cyclohexane  polymerization temperature:       50° C. Me.sup.2+ : Ba.sup.2+ or Ca.sup.2+                         

EXAMPLE 5

The effect of the mole ratio of Mg/Al in organometallic complexes ofmagnesium and aluminum on percent polybutadiene microstructure is shownin Table IV, below. The Mg-Al-Ba catalysts were prepared according toExample 1 at constant Ba/Mg mole ratio of about 1/5. A controlpolymerization of butadiene with (sec-C₄ H₉)Mg(n-C₄ H₉) in combinationwith a barium salt prepared according to Example 1 resulted in atrans-1,4 content of 67%, in the absence of Et₃ Al. A trans-1,4 contentof only 81% was obtained in polymers made with a Ba-MgAl complex atMg/Al=105/1 (MAGALA-DNHM, Texas Alkyls, Inc.) catalyst (Run 20). Nopolymerization of butadiene occurred with a barium salt in combinationwith MAGALA-0.5E (Mg/Al=1/2) (Runs 14, 15 and 16 below). The highestdegree of stereoregularity was obtained with complexes of barium saltswith MAGALA-6E or MAGALA-7.5E (Runs 17 and 18). The trans-1,4 contentsin these polybutadienes were 89% with 2% or 3% vinyl unsaturation.

                                      TABLE IV                                    __________________________________________________________________________    Effect of Mg/Al Mole Ratio in Mg--Al Complexes                                on Microstructure of Polybutadiene                                                                          % Diene                                         Run                                                                              Organometallic                                                                              Mole Ratios  Structure                                       No.                                                                              Complex of Mg and Al                                                                        Mg/Al                                                                             Ba/Mg                                                                              Al/Ba                                                                             Trans                                                                              Vinyl                                      __________________________________________________________________________    14.sup.a                                                                         1(n-Bu).sub.2 Mg.2(Et).sub.3 Al                                                             0.54                                                                              0.19 9.70                                                                              No Poly-                                                                      merization                                      15.sup.a                                                                         1(n-Bu).sub.2 Mg.2(Et).sub.3 Al                                                             0.54                                                                              0.29 6.40                                                                              No Poly-                                                                      merization                                      16.sup.a                                                                         1(n-Bu).sub.2 Mg.2(Et).sub.3 Al                                                             0.54                                                                              0.61 3.00                                                                              No Poly-                                                                      merization                                      17.sup.b                                                                         5.4(n-Bu).sub.2 Mg.1(Et).sub.3 Al*                                                          5.4*                                                                              0.19 0.97                                                                              89   2                                          18.sup.b                                                                         7.6(n-Bu).sub.2 Mg.1(Et).sub.3 Al#                                                          7.6#                                                                              0.16 0.82                                                                              89   3                                          19.sup.b                                                                         27(n-hexyl).sub.2 Mg.1(Et).sub.3 Al                                                         27.0                                                                              0.22 0.17                                                                              .sup. 83.sup.c                                                                     .sup. 4.sup.c                              20.sup.b                                                                         105(n-hexyl).sub.2 Mg.1(Et).sub.3 Al.sup.d                                                  105.0                                                                             0.22 0.04                                                                              81   4                                          21.sup.b                                                                         (sec-Bu)Mg(n-Bu)                                                                            No Al                                                                             0.12 0   67   10                                         __________________________________________________________________________     .sup.a polymerizations were carried out in nhexane at 65° C.           .sup.b polymerizations were carried out in cyclohexane at 50° C.       .sup.c estimated values from infrared spectrum of polymer film.               .sup.d MAGALA DNHM, Texas Alkyls, Inc.  din-hexyl magnesium containing 1-     mole % Et.sub.3 Al relative to the Mg compound.                               *MAGALA6E; 5.4 ratio as analyzed.                                             #MAGALA7.5E; 7.6 ratio as analyzed.                                      

EXAMPLE 6

The effect of the mole ratio of barium(t-decoxide-t-butoxide-hydroxide),prepared according to Example 1, to dibutylmagnesium in MAGALA-6E onpolybutadiene microstructure and molecular weight is summarized in TableV, below. The polymerization charge was the same as given in Run 1 ofExample 2. FIG. 2 shows that the amount of trans-1,4 structure isincreased to a maximum of about 90% as the mole ratio of Ba²⁺ /Mg²⁺ isdecreased from 1.0 to about 0.2. Concurrently, the vinyl contentdecreased from 7% to 2%. No polymerization of butadiene was observed incyclohexane at 50° C. after 3 days with MAGALA-6E alone or with a moleratio of Ba²⁺ /Mg²⁺ =0.05.

Polybutadienes prepared with mole ratios of Ba²⁺ /Mg²⁺ equal to 0.2 arecharacterized by trans-1,4 contents of about 90%, crystalline melttemperatures of 43° C. and 70° C., intrinsic viscosities of about 2.0 intoluene at 25° C., and absence of gel.

                                      TABLE V                                     __________________________________________________________________________    Effect of Mole Ratio of Barium Salts to                                       (Bu).sub.2 Mg in Mg--Al--Ba Catalyst on                                       Molecular Structure of Polybutadiene                                          __________________________________________________________________________                    %       % Diene Crystalline                                                                         tol                                     Run                                                                              Mole Ratios  Conversion                                                                            Structure                                                                             Melting                                                                             [η]25                               No.                                                                              Ba.sup.2+ /Mg.sup.2+                                                                 Al.sup.3+ /Ba.sup.2+                                                                (hours) Trans                                                                             Vinyl                                                                             Temp., °C.                                                                   dl/g                                    __________________________________________________________________________    22 0      0     No apparent                                                                           --  --  --    --                                                      pzn. of                                                                       butadiene                                                                     with                                                                          MAGALA-6E,                                                                    alone                                                         23 0.05   3.91  No apparent                                                                           --  --  --    --                                                      pzn.                                                                          (72 hours)                                                    24 0.11   1.67  63 (72) 87  2   36, 60                                                                              2.35                                     1 0.20   0.85  100 (91)                                                                              89  2   43, 70                                                                              2.11                                    25 0.30   0.62  96 (72) 79  3   -9, 33                                                                              2.26                                    26 0.52   0.35  99 (74) 73  4   -16, 24                                                                             1.82                                    27 1.00   0.18  94 (44) 64  7   -15   0.82                                    __________________________________________________________________________    Polymerization Conditions:                                                                  1.                                                                             Polymerizations were carried out                                              in cyclohexane at 50° C.                                             2.                                                                              Molar concentrations of butadiene                                             and (Bu).sub.2 Mg were approximately:                                         [Butadiene].sub.o = 2.4;                                                      [(Bu).sub.2 Mg].sub.o = 2.8 × 10.sup.-3                  __________________________________________________________________________

EXAMPLE 7

The catalyst complex of MAGALA-6E andbarium(t-decoxide-t-butoxide-hydroxide), Example 1, was used to preparepolybutadienes according to Example 2, in n-hexane and toluene, as wellas cyclohexane. The structural analysis, as shown in Table VI, below,shows that a high trans-1,4 polybutadiene was formed in these solvents.A slightly lower trans-1,4 content and intrinsic viscosity were obtainedfor the polymer prepared in toluene.

                  TABLE VI                                                        ______________________________________                                        Effect of Solvent on the Molecular Structure of                               Butadiene Based Polymers Prepared with Ba[(t-RO).sub.2-x (OH).sub.x ]         5.4 (n-Bu).sub.2 Mg.1(Et).sub. 3 Al (MAGALA-6E)                               Catalyst Composition of Example 1.                                            Polymerization Temp. = 50° C.                                                           %      % Diene   tol  Crystalline                            Run  Polymerization                                                                            Sty-   Structure [η]25                                                                          Melting                                No.  Solvent     rene   Trans Vinyl dl/g Temp., °C.                    ______________________________________                                        28   n-hexane    8      88    2     2.02 23, 34                                1   Cyclohexane 0      89    2     2.11 43, 70                               29   Toluene     0      85    3     1.84 24, 36                               ______________________________________                                    

It, also, is possible to prepare polybutadienes in cyclohexane at 50° C.with trans-1,4 contents of 88% (3% vinyl) with Mg-Al-Ba catalystsobtained by combining barium (t-alkoxide-hydroxide) with (sec-C₄H₉)Mg-(n-C₄ H₉) and C₂ H₅)₃ Al, instead of the commercial MAGALA, inmole ratios of Mg/Al of 2 to 3 and Ba/Mg of 0.20. An increase in Mg/Almole ratio (at constant Ba/Mg) from 3 to 6 to 15 to 25 results in adecrease in trans-1,4 content from 88% to 86% to 83% to 80%.

EXAMPLE 8

Table VII, below, compares the temperature dependence for SBR's preparedwith the Mg-Al-Ba catalyst composition of Example 1 in cyclohexane.Trans-1,4 content increased from 83% to 90% as polymerizationtemperature decreased from 75° C. to 30° C. The increase in trans-1,4content with decreasing polymerization temperature occurred withcorresponding decreases in both vinyl and cis-1,4 contents. It is to benoted that high trans-1,4 SBR's can be prepared over a fairly wide rangeof polymerization temperatures with this catalyst system.

                  TABLE VII                                                       ______________________________________                                        Effect of Polymerization Temperature on                                       Molecular Structure of High Trans SBR                                              Wt. %   Polymerization                                                                            % Con- % Diene   tol                                 Run  Sty-    Temperature version                                                                              Structure [η]25                           No.  rene    (°C.)                                                                              (hours)                                                                              Trans Vinyl dl/g                              ______________________________________                                        30    6.5    30          55 (172)                                                                             90.0  1.6   0.88                              31   17.0    50          86 (118)                                                                             88.0  2.1   1.60                              32   22.0    65          95 (119)                                                                             85.6  3.1   1.54                              33   23.2    75          92 (23)                                                                              82.9  3.7   1.49                              ______________________________________                                         Mole Ratio: Ba/Mg = 0.20                                                 

EXAMPLE 9

The concentration of the Mg-Al-Ba catalyst composition of Example 1 withconstant Ba²⁺ /Mg²⁺ ratio (0.20) has a marked effect on the trans-1,4content of polybutadiene, as shown in Table VIII, below. The trans-1,4content approaches a limiting value of about 90% as the molar ratio ofbutadiene to dibutylmagnesium decreases from 1549 to 795. The intrinsicviscosity increases with an increase in this ratio suggesting that thepolymer molecular weight is controlled by the ratio of grams ofbutadiene polymerized to moles of catalyst charged.

                                      TABLE VIII                                  __________________________________________________________________________    Effect of Catalyst Concentration on Molecular Structure                       of Polybutadiene Prepared with Mg--Al--Ba Catalyst                               Initiator     Initial                                                         Charged  Bd   Molar Ratio                                                                           %   % Diene tol                                      Run                                                                              (mM)     Charged                                                                            [Bd].sub.o /                                                                          Conv.                                                                             Structure                                                                             [η]25                                No.                                                                              Ba Salt                                                                           (Bu).sub.2 Mg                                                                      (grams)                                                                            [(Bu).sub.2 Mg].sub.o                                                                 (hrs.)                                                                            Trans                                                                             Vinyl                                                                             dl/g                                     __________________________________________________________________________    7  0.36                                                                              1.76 28.5 299      90 90  3   1.38                                                      (--M.sub.n = 8,100).sup.a                                                             (43)                                                 1  0.14                                                                              0.63 27.1 795     100 89  2   2.11                                                      (--M.sub.n = 21,500).sup.a                                                            (91)                                                 34 0.07                                                                              0.29 24.3 1549    100 80  3   4.29                                                      (--M.sub.n = 41,900).sup.a                                                            (96)                                                 __________________________________________________________________________     Solvent: cyclohexane. Temperature: 50° C. Mole Ratio: Ba/Mg = 0.20     .sup.a --Mn calculated from grams of BD charged to gramequivalents of Mg      charged (carbonMg).                                                      

EXAMPLE 10

FIG. 4 shows that the MWD of high trans SBR (15% styrene) can bebroadened (changed or controlled) by chain extension with divinylbenzene(DVB). DVB was added at 87% conversion, and the linking reaction ofchain ends with DVB (mole ratio of DVB/Mg=1.0) was carried out incyclohexane at 82° C. for 6 hours.

The shape of the MWD of the linear precursor SBR (Run 35) is fairlynarrow with a small fraction of low molecular weight tailing.Heterogeneity indices (MHD w/MHD n) of 2.0 to 3.0 (estimated by GPC) arerepresentative values of these linear SBR's. A comparison of the shapesof the MWD curves in FIG. 4 shows a buildup in the amount of highmolecular weight polymer and an increase in molecular weight as a resultof linking of chain ends with DVB.

High trans SBR's chain extended with DVB can be oil extended. They haveless cold flow (Table IX below) and improved mill processibilitybehavior relative to linear high trans SBR's. FIG. 5 compares therheological behavior of a linear high trans SBR of this invention and acorresponding SBR chain extended with DVB. Measurements of complexviscosity (η*) of these raw polymers at various shear rates wereobtained with a Rheometric Mechanical Spectrometer at 90° C. with aneccentric rotating disc (ERD). It can be seen that the chain extendedSBR shows higher viscosity at low shear rates and lower viscosity athigh shear rates than the linear control polymer. This informationcorrelates well with the lower cold flow of high trans SBR chainextended with DVB.

                                      TABLE IX                                    __________________________________________________________________________    Effect of Chain Extension of                                                  High Trans SBR on Cold Flow                                                        Wt. %  tol                  Cold Flow                                         Styrene in                                                                           [η]25                                                                         --M.sub.w /--M.sub.n                                                                Oil Content                                                                         ML-4 at 50° C.                             Run No.                                                                            Composition                                                                          dl/g                                                                              (by GPC)                                                                            (phr) (100° C.)                                                                   (mg/min.).sup.c                              __________________________________________________________________________    35.sup.a                                                                           15     1.58                                                                              3.7   0     48   20.0                                         36.sup.a                                                                           20     1.58                                                                              --    0     --   11.9                                         37.sup.b                                                                           15     1.95                                                                              3.2   14    40   3.4                                          38.sup.b                                                                           22     2.20                                                                              Bimodal                                                                             0     --   0                                            39.sup.b                                                                           21     2.20                                                                              Bimodal                                                                             37.5    41.5                                                                             1.0                                          __________________________________________________________________________     .sup.a linear SBR, unextended.                                                .sup.b SBR's chain extended with divinylbenzene (DVB) after 80-90%            conversion.                                                                   .sup.c Phillips Chem. Co. Method WATB 5.01.20 of December 1, 1961.       

EXAMPLE 11

An SBR, prepared by the process of the present invention and containing14.8% styrene with 84.5% trans-1,4 placements in the polybutadieneportion, was cured in the absence of fillers with 1% dicumyl peroxide.The crystalline melt temperature of the peroxide cross-linked SBR was18° C., obtained on a Perkin-Elmer DSC-II instrument. The cured rubberfilm was mounted in the unstretched state on an x-ray unit. The samplewas subjected to x-ray analysis using CuKα radiation and a nickel filterat room temperature. As shown in FIG. 6, this SBR gum vulcanizate in theunstretched state exhibited a diffuse halo characteristic of anon-crystalline material. At 200% strain, a diffraction pattern oforiented crystalline polymer (equatorial arcs) was observed. Severaloff-axial reflections appeared in the X-ray scan in addition to theequatorial fiber arc as the sample was elongated to 700%. This resultdemonstrates the ability of this rubber to undergo strain-inducedcrystallization. Building tack and green strength are properties oftencharacteristic of a crystallizable elastomer such as natural rubber. Itwill be demonstrated in the following examples that this set ofproperties is also characteristic of the SBR's of this invention.

With respect to FIG. 6 the following information is given:

    ______________________________________                                                Sample                                                                        %         Hours    Distance of Polymer Sample                         Photograph                                                                            Elongation                                                                              Exposure to X-ray Film, Approx.                             ______________________________________                                        A        0         4       30 mm.                                             B       200       12       30 mm.                                             C       700        6       50 mm.                                             D       700       17       50 mm.                                             ______________________________________                                    

EXAMPLE 12

Green strength is a quality that is possessed by natural rubber and isessentially absent in emulsion SBR. In fact, very few synthetic rubbershave green strength comparable to natural rubber. Green strength is ameasure of the cohesiveness in stretched, uncured rubber. The presenceof green strength in a rubber prevents the occurrence of thinning downand breaking during fabrication of an uncured tire. It is generallyaccepted that the green strength of natural rubber arises fromstrain-induced crystallization.

Green strength has been measured for an uncompounded high trans SBRprepared with the Mg-Al-Ba catalyst of this invention. The SBR contained20% styrene with 88% trans-1,4 polybutadiene placements and exhibited acrystalline melting temperature of 22° C., as measured by DTA. Greenstrength data was obtained from stress-strain measurements onunvulcanized polymers with an Instron tester at room temperature. Thecrosshead speed was 50.8 cm/minute. Sample specimens were prepared bypress molding tensile sheets at 121° C. for 5 minutes with a ram forceof 11360 kg. The data in Table X, below, demonstrate that the greenstrength (0.95 MPa) of the uncompounded and uncured experimental hightrans SBR of this invention was equivalent to natural rubber (MV-5)(peptized No. 3 ribbed smoked sheets; uncured and uncompounded).

The stress-strain curves of uncured, compounded (45 phr HAF carbonblack) high trans SBR (15% styrene) with 85% trans content of thisinvention are compared with natural rubber (SMR-5) and an emulsion SBRin FIG. 7. The green tensile strengths of NR and high trans SBR arenearly equivalent (1.4 MPa). The stress-strain curves of NR and theexperimental high trans SBR of this invention have positive slopes above150% elongation relative to a negative slope in the stress-strain curveof emulsion SBR (SBR-1500). The presence of a positive slope can betaken as evidence for strain-induced crystallization.

                  TABLE X                                                         ______________________________________                                        Comparison of Green Tensile Strength of                                       Unfilled, Uncured High Trans SBR with Natural Rubber                                         Run No.                                                                       40                                                                            Natural                                                                              36                                                                     Rubber High Trans SBR                                                         (MV-5) (20% Styrene)                                           ______________________________________                                        Mooney Viscosity 72       30                                                  ML-4 (100° C.)                                                         Tensile Strength                                                              PSI              139      138                                                 MPa              0.96     0.95                                                Elongation at break, %                                                                         633      1395                                                ______________________________________                                    

EXAMPLE 13

Tack strength is defined as the force required to separate two uncuredpolymer surfaces after they have been brought into contact. The limitingtack strength of a rubber is necessarily its green strength, or theforce required for its cohesive failure. Although high green strength isnecessary, it is, by itself, insufficient to insure good tack. High tackstrength is an especially desirable property in the fabrication ofarticles, especially those having a complex geometry, prior tovulcanization.

Tack strength was measured using the Monsanto Tel-Tak machine. The testspecimens were raw and compounded polymers pressed between Mylar film at100° C. Two 0.64 cm×5.08 cm diecut sample strips were placed at rightangles to each other and retained in special sample clamps. A fixedload, 0.221 MPa, was then applied for 30 seconds. The samples werepulled apart at a constant separation rate of 2.54 cm/minute. The testwas run at room temperature. The true tack values reported in Table XI,below, represent the difference between the apparent tack (rubber versusrubber) and the value obtained for rubber versus stainless steel. Theresults in Table XI for several uncompounded and uncured rubbers showthat the apparent tack strength of high trans SBR (0.28 MPa) of thisinvention is higher than natural rubber.

The presence of carbon black (45 phr HAF) in formulations of high transSBR (15% styrene, 85% trans) of this invention and NR (SMR-5) resultedin an increase in tack strength, as shown by comparing data in Tables XIand XII, below. The compounded tack strength of high trans SBR of thisinvention is equivalent to NR within experimental error. The tackstrength of a blend of equal amounts of high trans SBR of this inventionand NR was slightly higher than the respective unblended polymers.

It is important in construction of tires that tack strength is developedquickly when two strips of rubber are brought into contact. FIG. 8 showsthat high tack strength is obtained for low contact times (6 seconds)for both high trans SBR of this invention and NR. Both rubbers have whatis often referred to as "quick-grab".

                  TABLE XI                                                        ______________________________________                                        Monsanto Tel-Tak of Uncompounded, Uncured Rubbers                                          Crystalline                                                                           Tack Strength.sup.a                                      Run  Polymer       Melting   Apparent                                                                              True                                     No.  Description   Temp., °C.                                                                       PSI  MPa  PSI  MPa                               ______________________________________                                        .sup. 39.sup.b                                                                     High Trans SBR                                                                              24        41   0.28 35   0.24                                   of this invention                                                             (21% styrene,                                                                 87% trans)                                                               40   Natural Rubber                                                                              28        34   0.23 32   0.22                                   (MV-5)                                                                   41   Trans-poly-    9        38   0.26 35   0.24                                   pentenamer                                                               42   High Trans SBR                                                                              -1        34   0.23 23   0.16                                   of this invention                                                             (23% styrene,                                                                 83% trans)                                                               43   Cis-1,4       -6        27   0.19 15   0.10                                   Polybutadiene                                                                 (99% cis)                                                                44   SBR-1500      None      22   0.15  4   0.03                                   (Emulsion).sup.c                                                                            Observed                                                   ______________________________________                                         .sup.a 30 seconds contact time, 32 oz. load.                                  .sup.b 37.5 phr Philrich 5 oil added to polymer.                              .sup.c BDSTY rubber, about 23.5% bound styrene, cold polymerized.        

                  TABLE XII                                                       ______________________________________                                        Monsanto Tel-Tak of Compounded, Uncured Rubbers                               ______________________________________                                                          Contact                                                                              Apparent                                                               Time   Tack Strength                                        Run No.                                                                              Polymer Description                                                                            (minutes)                                                                              PSI   MPa                                    ______________________________________                                        45     High Trans SBR   0.5      52    0.36                                          (15% styrene, 85% trans)                                                                       3.0      69    0.48                                                           6.0      69    0.48                                   46     Natural Rubber   0.5      65    0.45                                          (SMR-5)          3.0      64    0.44                                                           6.0      67    0.46                                   47     Blend of 50/50   0.5      71    0.49                                          High Trans SBR/NR                                                                              3.0      69    0.48                                          (SMR-5)          6.0      73    0.50                                   ______________________________________                                        Formulation for the Above Compounded but Uncured Rubber,                      Parts by Weight                                                                          High Trans                                                         Ingredient SBR         NR     Blend                                           ______________________________________                                        Polymer    100         100    50/50,                                                                        NR/High Trans SBR                               HAF Carbon 45          45     45                                              Black                                                                         Oil        5 Naphthenic                                                                              0      7 Naphthenic                                    ZnO/Stearic Acid                                                                         5/3         5/3    5/3                                             Antioxidant                                                                              2           2      2                                               Tackifier 775                                                                            3           3      3                                               Sulfur     1.0         1.0    1.0                                             Total Accelerator                                                                        1.8         1.8    1.8                                             ______________________________________                                    

EXAMPLE 14

A high trans SBR of this invention was prepared according to Run No. 2in Example 2. The resulting copolymer contained 20% styrene with 86%trans-1,4 content in the polybutadiene portion. The intrinsic viscosityin toluene at 30° C. was 1.82 dl/g. The copolymer showed a crystallinemelt temperature of 20° C. in the DTA thermogram.

A description of the compound recipe and cure conditions for the aboveSBR along with a commercial butadiene-styrene copolymer (SBR-1500) andnatural rubber (SMR-5) is given in Table XIII, below. Satisfactory ratesof cure in the SBR's were obtained with a sulfur cure accelerated with2-(morpholino) thiobenzothiazole (NOBS Special) and tetramethylthiurammonosulfide (TMTM). A comparison of the physical properties for theserubbers is given in Table XIV, below.

It should be noted that high trans SBR has higher tear strength thanSBR-1500. This can be related to strain-induced crystallization in thehigh trans SBR. It is clear that the vulcanizate properties of hightrans SBR approach those of natural rubber.

                  TABLE XIII                                                      ______________________________________                                                  Formulations (PHR)                                                                    Natural                                                                       Rubber    High Trans SBR                                              SBR-1500                                                                              (SMR-5)   (20% Styrene)                                               Run No.:                                                            Ingredients 48        49        50                                            ______________________________________                                        Rubber      100       100       100                                           Antioxidant 2246.sup.a                                                                    2         2         .sup. 4.sup.e                                 Zinc Oxide  5         5         5                                             Stearic Acid                                                                              3         3         3                                             Atlantic Wax                                                                              3         3         --                                            Tackifier 775.sup.b                                                                       3         3         3                                             HAF Carbon Black                                                                          45        45        42                                            PHILRICH 5 Oil                                                                            5         5         14.sup.f                                      (Phillips Pet.)                                                               NOBS.sup.c  1.6       0.5         1.6                                         TMTM.sup.d  0.2       --          0.2                                         CRYSTEX Sulfur.sup.g                                                                      1.3       2.5         1.3                                         (Stauffer Chem.)                                                              Cured, min./°C.                                                                    45/142    35/142    21/142                                        ______________________________________                                         .sup.a 2,2methylenebis (4methyl-6-tert-butylphenol)                           .sup.b octylphenol formaldehyde (nonheat reactive)                            .sup.c 2(morpholino) thiobenzothiazole (American Cyanamid)                    .sup.d tetramethylthiuram monosulfide                                         .sup.e 2 phr, N--(1,3dimethylbutyl)-N'--phenylp-phenylene diamine and 2       phr, N,N'--Bis(1,4dimethylpentyl)-p-phenylene diamine                         .sup.f Naphthenic Oil (Circosol 42XH, Sun Oil Co.)                            .sup.g CRYSTEX contains 80% sulfur in mineral oil                        

                  TABLE XIV                                                       ______________________________________                                        Comparison of Properties of High Trans SBR of This                            Invention with SBR-1500 (Emulsion Polymer) and                                Natural Rubber                                                                            Run No.                                                                                49       50                                                          48       Natural  High Trans                                                  SBR-1500 Rubber   SBR                                             ______________________________________                                        Modulus at 100%, MPa                                                                        1.51       1.50     1.38                                        Modulus at 300%, MPa                                                                        6.47       7.34     3.68                                        Tensile Strength, MPa                                                                       21.94      25.23    20.13                                       Elongation, % 700        650      770                                         Hardness, Shore A                                                                           66         59       63                                          Tear Strength,                                                                              83         123      112                                         Crescent, kN/m                                                                Goodrich Heat Buildup                                                                       32         28       28                                          (100° C.), ΔT °C.                                         Perm. Set, %  10.2       18.6     6.4                                         (100° C.)                                                              DeMattia No. of                                                                             100        100      100                                         Flexes × 10.sup.-3                                                      Crack Growth, %                                                                             100        41       75                                          ______________________________________                                    

EXAMPLE 15

To n-butylethyl magnesium (Texas Alkyls, Inc., BEM, a mixture ofn-butylethyl magnesium and triethyl aluminum, mole ratio of Mg to Al of50:1, in heptane) was added cyclohexane and additional triethyl aluminumto give a mole ratio of Mg/Al=4.8 to 1. To the Mg-Al composition wasadded

    Ba[(t-C.sub.10 H.sub.21 O).sub.0.96 (t-C.sub.4 H.sub.9 O).sub.0.96 (OH).sub.0.08 ]

in toluene to provide a mole ratio of Ba/Mg=0.26. The resulting Ba-Al-Mgcatalyst complex was then used to polymerize propylene oxide (PO) at 80°C. to obtain a tacky solid. The polymerization conditions used were asfollows:

    ______________________________________                                                                   Grams PO  %                                        PO    Solvents, grams      Per mM    Conv.                                    Grams Cyclohexane                                                                              Heptane  Toluene                                                                              Mg      (Hrs).                               ______________________________________                                        40.2  8.8        3.8      19.1   10.9    40(64)                               ______________________________________                                    

The tacky polypropylene oxide solid (14% by weight of total polymer) inthe acetone-insoluble fraction (at -15° C.) showed a broad endothermwith crystalline melt peak at 46° C. by DTA and a Tg of -80° C. andexhibited an intrinsic viscosity in toluene at 30° C. of 3.17 dl/g (5%by weight insolubles). A 3/1 ratio of isotactic to syndiotacticplacements was found by ¹³ C NMR.

EXAMPLE 16

A. To BEM (Texas Alkyls, Inc., a mixture of n-butylethyl magnesium andtriethylaluminum having a mole ratio of Mg to Al of 50:1 in heptane) wasadded additional triethylaluminum to give a BEM mixture with a moleratio of Mg to Al of 5:1. To the resulting BEM mixture was added abarium salt in toluene prepared according to Example 1(a), above. Themole ratio of Ba to Mg was 0.19. The mixture of the magnesium, aluminumand barium compounds was then charged to a reactor containing hexane andunder an argon atmosphere. Butadiene was then charged to the reactor.The ratio of the butadiene to the BEM per se was 17.5 g butadiene permmole of the BEM. Polymerization was conducted for 43 hours at 50° C. toa conversion of 93%. Polymerization was terminated with methanol. Theresulting polymer exhibited a M by membrane osometry of 34,000 and anintrinsic viscosity in dl/g in toluene at 30° C. of 0.84.

B. Run A, above, was repeated except that the ratio of the butadiene tothe BEM per se was 18.8 grams of butadiene per mmole of BEM, theconversion of butadiene to homopolybutadiene was 94% (estimated) and thepolymerization was not terminated. Thereafter, divinyl benzene (DVB) wasadded to the reactor containing the solution of the non-terminatedpolybutadienyl carbanion. The mole ratio of the DVB to the BEM per sewas 2.4. The total grams of butadiene added was 17.19 and of DVB was0.28. Polymerization was then conducted at 60° C. for an additional 19hours. Polymerization was terminated with methanol. Total polymerizationtime was 62 hours. The final conversion was 96%. The microstructure ofthe butadiene segments of the resulting DVB linked polymer was 89%trans, 2% vinyl and 9% cis. The M by membrane osometry was 109,000 andthe intrinsic viscosity in dl/g at 30° C. in toluene was 1.87. Acomparison of the number-average molecular weight, M, of the linearpolymer (A.) with that of the DVB-linked polybutadiene (B.) demonstratesthe successful preparation of a star polymer having an average of threearms. FIG. 9 shows MWD curves of this DVB-linked polybutadiene and itsprecursor polybutadiene. It is apparent that a substantial amount ofDVB-linked polybutadiene was formed.

EXAMPLE 17

A mixture or complex was prepared by mixing together dibutylmagnesium(in heptane), triethylaluminum (in hexane) and the barium salt ofExample 1(a), above (in cyclohexane). The mole ratio of the Mg to the Alwas 7.5, and the mole ratio of the Ba to the Mg was 0.17. The Mg-Al-Bamixture was then charged to a reactor containing cyclohexane and underan argon atmosphere. 32.7 g of styrene were then charged to the reactor(ratio of styrene to Mg was 21.7 g styrene per mmole Mg). Polymerizationwas conducted for 66 hours at a temperature of 60° C. to a conversion of77% to polystyrene (as determined by sampling).

Then 48 grams of butadiene were added to the reactor containing thesolution containing the non-terminated polystyryl carbanion and 7.5 g ofstyrene monomer. The ratio of Bd+Sty to Mg was 53.6 g of Bd+Sty permmole of Mg. The polystyryl carbanion was used to initiate thecopolymerizaton of butadiene with styrene. Polymerization was thencontinued at 60° C. for an additional 96 hours to provide anon-terminated poly [styrene-b-(styrene-co-butadiene)] block copolymer.By sampling conversion was determined to be 90.6%.

Thereafter, 0.64 gram of divinyl benzene was added to the reactor toreact with the non-terminated poly[styrene-b-(styrene-co-butadiene)].The mole ratio of DVB/Mg was 3.2 (ratio of monomers to Mg was total of53.95 grams of Sty+Bd+DVB per mmole of Mg). Polymerization was thenconducted at 60° C. for an additional 24 hours for a grand total of 186hours. Polymerization was terminated with methanol, and the conversionwas found to be 100%. The resulting product contained 42 wt. % styreneand the microstructure of the butadiene units was 84% trans, 6% vinyland 10% cis.

FIG. 10 shows GPC chromatograms of the DVB-linkedpoly[Sty-b-(Sty-co-Bd)] and the corresponding two linear precursors. Therelative shapes of the curves in FIG. 10 demonstrate both an increase inthe amount of high molecular weight polymer as well as an increase inthe molecular weight as a result of the reaction of active chain endswith DVB. It is apparent that a certain fraction of unlinked polystyreneand poly(Sty-co-Bd) is present along with star polymer. However, the DVBlinking reaction produces a sufficient amount of "reinforcing"polystyrene domain structure to provide elastomer strength. This can beseen by the shape of the stress-strain curve (FIG. 11) for thecompression molded sample. A stress value of 8.3 MPa (1200 psi) at break(1100% elongation) was obtained for this DVB-likedpoly[Sty-b-(Sty-co-Bd] material.

We claim:
 1. The method which comprises polymerizing under inertconditions in a hydrocarbon solvent at a temperature of from about 0° to150° C. a polymerizable monomer selected from the group consisting of(A) butadiene-1,3 and (B) at least 50% by weight of butadiene-1,3 andthe balance essentially styrene with a catalyst in a minor effectiveamount sufficient to polymerize said monomer to obtain high transhomopolymers, random copolymers or block copolymers, said catalystcomprising (1) an alcoholate selected from the group consisting ofbarium alcoholate, calcium alcoholate and strontium alcoholate andmixtures thereof, (2) an organoaluminum compound selected from the groupconsisting of alkyl and cycloalkyl aluminum compounds and mixtures ofthe same in which the organic moieties have from 1 to 20 carbon atomsand (3) an organomagnesium compound selected from the group consistingof alkyl and cycloalkyl magnesium compounds and mixtures of the same inwhich the organic moieties have from 1 to 20 carbon atoms, where the molratio computed as metal of barium, calcium and/or strontium to magnesiumis from about 1:10 to 1:2 and where the mol ratio computed as metal ofmagnesium to aluminum is from about 105:1 to 1.5:1 and at about 85%conversion of said monomer to said polymer adding from about 0.01 to10.0 parts by weight of a chain extender or branching compound selectedfrom the group consisting of divinyl aromatic and trivinyl aromaticcompounds per 100 parts by weight of said monomer initially charged toobtain a chain extended, branched or star polymer.
 2. The methodaccording to claim 1 where said chain extender or branching compound isdivinylbenzene.
 3. The method according to claim 1 additionally addingto or copolymerizing with said chain extended, branched or star polymera copolymerizable polar material selected from the group consisting ofthe acrylates, the alkacrylates, the nitriles, the epoxides, thesiloxanes and the lactones in an amount up to about 30 parts by weightbased on 100 parts by weight of said chain extended, branched or starpolymer.
 4. The method according to claim 3 where said chain extender orbranching compound is divinyl benzene, said polar material is methylmethacrylate and M is barium.
 5. The method according to claim 2 wheresaid polymerizable monomer is (A).
 6. The method according to claim 2where said first named copolymer comprises a random copolymer ofbutadiene-1,3 and styrene.
 7. The method according to claim 2 where saidfirst named copolymer comprises a block copolymer of butadiene-1,3 andstyrene.
 8. The method according to claim 2 where said first namedcopolymer comprises a poly(styrene-b-(styrene-co-butadiene-1,3) blockcopolymer.
 9. The method which comprises polymerizing under inertconditions in a hydrocarbon solvent at a temperature of from about 30°to 100° C. a polymerizable monomer selected from the group consisting of(A) butadiene-1,3 and (B) at least 50% by weight of butadiene-1,3 andthe balance essentially styrene with a catalyst composition in a minoreffective amount sufficient to polymerize said monomer to obtain hightrans homopolymers, random copolymers or block copolymers, said catalystcomposition comprising(1) at least one of ##STR7## where the mol ratioof a to b is from about 100:0 to 80:20, where M is at least one metalselected from the group consisting of Ba, Ca and Sr, where R is selectedfrom the group consisting of alkyl and cycloalkyl radicals of from 1 to6 carbon atoms which may be the same or different, where R' is an alkylradical of from 1 to 4 carbon atoms which may be the same or differentand where R" is a hydrocarbon radical having a molecular weight of fromabout 250 to 5,000, (2) R₃ ^(III) Al where R^(III) is selected from thegroup consisting of alkyl and cycloalkyl radicals of from 1 to 20 carbonatoms which may be the same or different and (3) R₂ ^(IV) Mg whereR^(IV) is selected from the group consisting of alkyl and cycloalkylradicals of from 1 to 20 carbon atoms which may be the same ordifferent, where the mol ratio of magnesium to aluminum of (2) and (3)computed as metal is from about 105:1 to 1.5:1 and where the mol ratioof M to magnesium of (1) and (3) computed as metal is from about 1:10 to1:2 and at about 85% conversion of said monomer to said polymers addingfrom about 0.01 to 10.0 parts by weight of a chain extender or branchingcompound selected from the group consisting of divinyl aromatic andtrivinyl aromatic compounds per 100 parts by weight of said monomerinitially charged to obtain a chain extended, branched or star polymer.10. The method according to claim 9 where said chain extender orbranching compound is divinylbenzene.
 11. The method according to claim9 additionally adding to or copolymerizing with said chain extended,branched or star polymer a copolymerizable polar material selected fromthe group consisting of the acrylates, the alkacrylates, the nitriles,the epoxides, the siloxanes and the lactones in an amount up to about 30parts by weight based on 100 parts by weight of said chain extended,branched or star polymer.
 12. The method according to claim 11 wheresaid chain extender or branching compound is divinyl benzene, said polarmaterial is methyl methacrylate and M is barium.
 13. The methodaccording to claim 10 where said polymerizable monomer is (A).
 14. Themethod according to claim 10 where said first named copolymer comprisesa random copolymer of butadiene-1,3 and styrene.
 15. The methodaccording to claim 10 where said first named copolymer comprises a blockcopolymer of butadiene-1,3 and styrene.
 16. The method according toclaim 10 where said first named copolymer comprises apoly(styrene-b-(styrene-co-butadiene-1,3) block copolymer.
 17. Theproduct produced by the method of claim
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